This application claims Paris Convention priority of DE 199 10 226.0 filed Mar. 9, 1999, the complete disclosure of which is hereby incorporated by reference.
The invention concerns a device and a method for characterizing and identifying an object, e.g. a container, with a surface visible from outside the object, onto which is disposed an optically readable one-dimensional bar code consisting of bars and spaces.
A device of this type and a corresponding method are known from the internet article xe2x80x9cBARCODExe2x80x9d by the company Stemmer Imaging GmbH, D-82178 Puchheim, http://www.cvc-imaging.com, last update 9. July 1998.
Bar codes belong to the group of optical codes and are widely used today. The arrangement of bars and spaces of varying widths can be found mainly on packings of all kinds. Thereon, the disposed bar code contains information e.g. about the producer, the product, use-by date, price, etc. But also in the industrial field, the use of bar codes offers advantages since the marking of products with bar codes can automate and/or accelerate production processes.
A patent application for the principle of bar code technology and the first bar code was filed in the U.S.A. in 1949. Due to the small number of electronic components available and corresponding high prices, application thereof was almost exclusively limited to the military. Only the introduction of microprocessors in 1970 allowed production of low-cost reading and processing devices which permitted longer operational times as compared with vacuum tube computers used up to then. The development of bar code technology experienced a real boost in 1982 when all objects used in connection with the army in the U.S.A. had to be provided with a bar code label for identification.
Due to the increasing variety of models, car manufacturers have also started to mark the different components for assembly and coordinated material supply.
A new advantage, in addition to fast and faultless data acquisition irrespective of the xe2x80x9cweak point human laborxe2x80x9d, is more and more the reduced price of corresponding bar code printing programs and also bar code reading devices.
Some terms are frequently used in connection with bar codes which will be briefly explained in the following. This list was taken roughly from the book xe2x80x9cBarcodexe2x80x94Einfxc3xchrung und Anwendungenxe2x80x9d (Bar codexe2x80x94introduction and use) by Mathias Pxc3x6tter and Ralf Jesse, Verlag Heinz Heise GmbH and Co. KG, Hannover, 1st edition 1993 and contains only the terminology required for understanding the present work.
A line or bar is the dark element of a bar code. Its binary value is one.
A space is a bright element of a code. Its value is zero.
The bars and spaces are arranged in parallel according to a defined pattern which, in total, contains machine-readable information.
Element
This term describes a bar as well as a space.
A module is the narrowest element of a code. Wide bars and spaces are calculated as a multiple of a module.
Module Width X
This value states the width of the narrowest element of a bar code, of the module, in millimeters.
Quiet Zone
The area between two bar codes has to be bright to indicate the start or end of the code to the reading device. This area is called the quiet zone.
Start and Stop Characters
Start and stop characters define a bar code. At the same time they ensure that bar codes can be read forwards and backwards. The start and stop characters of the bar codes are usually designed such that when they are read from the left to the right their sequence differs from that read from the right to the left. Some bar codes use so-called marginal characters instead of the usual start and stop characters.
Check-sum Digit
Bar codes may be provided with one or more check-sum digits for improving detection of decoding errors. Some codes demand the use of check-sum digits.
Tolerance
To permit correct reading of bar codes, only small tolerances from the nominal width or height are allowed. The tolerances are selected such that the bar code elements of differing widths can always be clearly delimited from one another. With many bar codes, sufficient distinction is achieved when wide bar code elements are two to three times as wide as narrow elements.
Ratio
This term is met only in connection with codes having two widths. The Ratio V states the relationship of the width of a broad element to the width of a narrow element (module).
In the course of time, many different bar code types were generated which were adapted to special applications.
One-dimensional Bar Codes
This type of bar code is the most widely used at the moment. Its design consists of a sequence of vertical, wider or narrower lines. One-dimensional bar codes are classified again into codes of two widths and multiple widths.
Codes of Two Widths
Two-widths code means that the elements of the bar code can assume only two different widths. This includes the code 2/5xe2x80x94family, the code Codabar and the code 39. Multiple-widths codes are e.g. code 93, code 128 and code EAN.
Bar codes are also widely used in science. A concrete new field of application can be found in the current production of the preparation robot NMRAutoPrep by the company Bruker Analytik GmbH which prepares samples for NMR spectroscopy and supplies same to an NMR spectrometer via a transport system.
The sample preparation is carried out automatically by the preparation robot by means of input analysis instructions. Correlation between the request and the sample is currently effected via a commercial bar code label disposed on the bottle.
The preparation robot NMRAutoPrep also offers the possibility of preparing samples for a BEST-NMR analysis (BEST-NMR=Bruker Efficiency Sample Transfer NMR). Thereby, the prepared sample is intermittently stored in 2 ml bottles of which up to 96 are located in a container, the so-called rack. This rack is then transmitted manually to a robot of the company Gilson which suctions the samples out of the bottles and supplies same to the probe head of the NMR magnet via a thin hose.
Up to now, the NMR analysis bottle could not be uniquely identified since mounting of a bar code label on the bottle is not possible due to the construction of the rack. The bar code label would be partly covered and for this reason the bottle would have to be lifted out of the rack and possibly turned. A one-dimensional bar code on the bottle lid would be larger than the diameter of the bottle (11 mm) and a two-dimensional bar code is also not possible due to the injection point (septum of rubber) in the center of the lid.
For this reason, the position of the bottle within the rack is stored and thereby provides correlation to the sample. It is, however, possible that bottles are mixed up during transport from the preparation robot NMRAutoPrep to the Gilson robot. For this reason, the current solution is not satisfactory.
In contrast thereto, it is the purpose of the present invention to present a device and a method for automatic detection, recognition and identification of objects, e.g. the above-mentioned bottles, which provide automatic identification of hollow, in particular hollow-cylindrical objects in as simple, technically undemanding and cheap manner as possible.
This object is achieved in accordance with the invention in that the bar code is disposed in an annular area of the bottle, that the bars and spaces extend in the shape of a star from a center of the annular area towards the outside and that the bar code is readable in the circumferential direction of the annular area.
A recess or a hole may thereby be provided inside of the annular area, e.g. the inlet opening of a bottle, and the structure outside of the annular area is unimportant for the inventive characterization. Since the bars and spaces of the bar code extend in a star-like manner radially outwardly, the bar code structured according to the invention can be read by optical scanning in the circumferential direction of the annular area, wherein the annular area does not have to be circular, but merely has to be a continuous annular surface. A continuous line extending in the circumferential direction of the annular area, to which the bars and spaces of the bar code according to the invention are essentially perpendicular, would be considerably longer, for identical surface of the annular area, compared to e.g. a line extending radially outwardly, with a bar code arranged annularly about the center in the annular area, such that the arrangement of the bar code according to the invention enables considerably higher information density.
In a preferred manner, the area containing the annular area is disposed on the upper side of a lid with which the container can be closed. Therefore, the inventive bar code can be easily read from the top without having to lift or possibly turn the container.
In a particularly preferred embodiment, the container is a bottle which is particularly suitable for demonstration of the advantages of the invention.
In a further development of this embodiment, the bottle is a sample bottle for spectroscopic analysis, in particular for nuclear magnetic resonance (=NMR) spectroscopy in an automated NMR analysis device using the above-described sample bottles as standard. The device according to the invention was particularly optimized especially for this purpose of use.
To improve characterization and identification of objects like e.g. hollow-cylindrical plastic sleeves, an advantageous embodiment of the device in accordance with the invention provides that the surface in the section enclosed by the annular area comprises a hole.
A further development is particularly preferred wherein the lid comprises a septum for injecting substances, the septum being enclosed by the annular area.
In this manner it is possible to store a large amount of information about the substance filled into the sample bottle, on the lid, wherein the annular surface for the bar code does not impair filling in the substance.
Advantageously, the automated NMR analysis device is comprised of a retaining device, in particular a retaining metal sheet, wherein the retaining device comprises a preferably circular window through which the bar code can be read. By means of the retaining device, the sample bottle can be held in a predetermined position through pressure on the lid.
In a particularly preferred embodiment, the annular area is an annulus as predetermined by the common geometrical shape of a bottle. An oval shape e.g. would not fit onto a conventional bottle opening or only incompletely utilize the space provided for characterization.
In a further advantageous embodiment the annular area is provided with a sector-shaped section as quiet zone of the bar code without any bars. This ensures reliable recognition of the beginning and end of the bar code.
One embodiment of the inventive device is of particular importance, wherein the bar code is disposed on a preferably self-adhesive label, in particular printed thereon. This enables easy and cheap printing e.g. by means of a standard printer connected to a PC.
In an alternative embodiment, the bar code may also be disposed directly onto the object to be characterized, in particular printed thereon, injection molded thereon, engraved or thermally disposed thereon. This increases the service life of the bar code and can usually not be removed afterwards which enables permanent reliable identification of the characterized object.
A further particularly preferred form of the inventive device is characterized by a reading means which can be moved, in particular rotated, relative to the bar code in the circumferential direction of the annular area for detecting the bar code. Thus, standard bar code reading means for reading out the inventive bar code can be used and complicated evaluation methods can be omitted.
A particularly cheap reading possibility is achieved by providing the reading means with a scanner including a reading pen.
In a further development the reading pen is stationary and the object to be identified with the bar code is movable relative to the reading pen. This avoids xe2x80x9ccable chaosxe2x80x9d of the electric supply to the reading pen during reading.
As an alternative, the object bearing the bar code may be held stationary during identification and the reading pen may be movable relative to the object. This allows simple handling of the objects since these may be held stationary during reading of the bar code.
A further alternative embodiment of the device according to the invention provides an image detection system with pattern recognition which can read the bar code in the annular area. Thereby, it is possible to hold the object to be identified bearing the inventive bar code and also the reading means in a stationary manner since reading does not require relative movement with respect to one another. Moreover, individual programming of the reading parameters may be carried out.
In a further preferred embodiment, the image acquisition system may acquire image data within a window and pass them on in digitized form to a computer with pattern-recognition software.
The image acquisition system preferably comprises a commercial xe2x80x9cCCD (charge coupled device) cameraxe2x80x9d which can currently be obtained at relatively low cost.
With respect to the method, the above-defined object of the invention is achieved in that for characterizing the object, the bar code is disposed in an annular area of the surface in such a manner that the bars and spaces extend in the shape of a star from a center of the annular range towards the outside and that the bar code for identifying the object is read out in the circumferential direction of the annular range.
One variant of the method in accordance with the invention is particularly preferred in which the bar code is disposed on the surface in a circular area between a predetermined minimum radius r1 and a predetermined maximum radius r2. This defines an inner minimum reading radius for maintaining tolerances.
Preferably, the bars and spaces of the bar code on a circle of a radius rx, wherein r1xe2x89xa6rxxe2x89xa6r2, correspond to the tolerances of a bar code specific standard, in particular the German industrial standard DIN EN 798,799, 800, 801.
When a reading means with scanner and reading pen is used, it is advantageous to read the bar code with the reading pen of the scanner in the circumferential direction of the annular area on a radius rL, wherein rxxe2x89xa6rLxe2x89xa6r2.
With the use of an image acquisition system with pattern recognition within a window, the following embodiment of the method in accordance with the invention is particularly preferred:
(a) Recording of an image, comprising at least the annular area, by means of the image acquisition system;
(b) Storing the recorded image in a digitized manner;
(c) Segmentation of the digitized image in the computer into associated bar code rings and allocation to individual object-related classes (=classification).
(d) Finding of the radially inner bar code limit on the radius r1 and of the radially outer bar code limit on the radius r2 for each object-related class;
(e) Reading of the bar code of each object-related class on a radius rL wherein rxxe2x89xa6rLxe2x89xa6r2;
(f) Decoding of the read bar code for each object-related class.
For elimination of interferences, a further development of this method variant is advantageous, in which a digital noise filter is applied to the image recorded in step (a), preferably after step (b).
One variant of the method is also preferred wherein the gray scale range of the image recorded in step (a) is spread and binarized which is also carried out preferably according to step (b). This makes the method less sensitive to possible changes in ambient light conditions.
To save time, the above-described method variants can be improved in that several annular areas of differing objects are recorded simultaneously in one single image in step (a).
A further improved method variant provides detection of all straight lines forming the respective image segment by means of Hough transformation in step (d) and that from the points of intersection of all detected straight lines, the center of gravity is calculated and identified as center of the bar code on the respective annular area. This enables reliable detection of the (virtual) center of the bar code in accordance with the invention.
A further improved method variant takes into consideration only the points of intersection in a predetermined window within the image segment. This allows suppression of disturbing straight lines at the edge of the annular section.
For ensuring reliable identification of the corresponding object, the following method steps are advantageous:
(e1) Reading of the bar code on a radius rL wherein rxxe2x89xa6rLxe2x89xa6r2;
(e2) Extraction of the quiet zone
(e3) Combination of pixels of the same color black or white;
(e4) Determination of the respective relative element width of the signals for bars or spaces of the bar code as a multiple of the thinnest bar or the thinnest space (=module);
(e5) Interpretation of the recognized pattern of bars and spaces as bar code and assignment to a corresponding known bar code type.
Safety can be further increased by reading the bar code on several differing radii rLxe2x80x2, rL41 . . . wherein rxxe2x89xa6rLxe2x80x2, rLxe2x80x3, . . . xe2x89xa6r2.
Further advantages of the invention can be derived from the description and the drawing. The features mentioned above and below may be used in accordance with the invention either individually or collectively in arbitrary combination. The embodiments shown and described are not to be understood as exhaustive enumeration, rather have exemplary character for describing the invention.
The invention is shown in the drawing and is explained in more detail by means of the embodiments.